It is known that various treatments of skin diseases or the like has been proposed and used over the years, mostly through topical application of linements, unguents or caustic agents such as nitric acid, chloracetic acid, salicylic acid, etc.
Moreover, for many years, the use of natural or synthetic polymers that have a relative affinity with skin tissues, have been employed as protective agents or as excipients and carriers for dermoreactive substances.
Prior products of external medical action, to be classified in the cathegory of liquid plasters for "spray" application, supply protection films, owing to evaporation of the solvent constituted to water or of water mixed with organic compatible solvents. Other similar products are mixed compositions of polymers and medicinal additives (emostatics, disinfectants, antibiotics; dermoprotectives). These prior products consist mostly of copolymers whose duration "in situ" after application, is of very few days, because of their sensitivity to water and perspiration. Their use is anyway suggested for the medication of wounds of small or medium dimensions, and the principal advantage of these materials is often limited to their easy use. Compounds belonging to this family have been also obtained with natural polymers of cellulosic kind, more or less chemically modified. Anyway, they are always products having a certain water sensitivity, that adhere to skin only through physical bonds.
In the literature of the field, it was mentioned also the use in exceptional cases of chemical unsaturated reactive substances, that, applied on serious wounds, with hemorrage danger, facilitate the arrest of the blood flow of wounds, due to a violent hemostatic action. These chemical substances are monomers of the cyanoacrylate family, that at skin contact, and by means of its humidity, polymerize, in that they are hydro-reactive products and chemically combined in correspondence to wounds.
Anyway, these products are not suitable for the normal epidermal and transdermal skin therapy, because of the absolute lack of elasticity and because of chemical toxicity, negative aspects that could be only accepted in drastic situations (serious wounds in war situations, mutilations, dangers of serious hemorrages).
Filmogenic polymers, endowed with hydrorepellent action, used in order to isolate recent wounds or sores, sensible to the soaking water effect, are recent introduction in the pharmaceutical field. Similar to the above mentioned polymers are for example alkylpolysiloxanes and other siliconic basis polymers that deposit upon skin through physical adhesion. They were used in the treatment of bedsores.
Of more recent vintage is the use of a polymer on the basis of animal collagen fibres, used alone or in combination in separate layers, with siliconic polymers, which always constitute the external protective layers.